1. Field of the Invention
The invention relates generally to communication systems between two units, where one unit controls transmission of the other unit and more particularly to the control of power levels associated with reverse mobile frame transmissions.
2. Description of the Related Art
Communication systems, such as Code Division Multiple Access (CDMA) systems and Time Division Multiple Access (TDMA) systems and the like communicate messages between infrastructure equipment and mobile units. As used herein, a forward message refers to a message generated by cellular infrastructure equipment and transmitted for reception by a mobile communication unit, and a reverse message refers to a message generated by a mobile communication unit such as a mobile cellular phone, to the cellular infrastructure equipment.
Power control is an important function in most communication systems, and is essential to the proper operation of second and third generation cellular systems of the DS-CDMA type. Power control is used to maintain sufficient communication link quality and information through put while using minimum power levels to maximum system capacity. Changing the power levels of the forward communication links used by a Base Transceiver Station (BTS) to transmit information to mobile stations is referred to as forward power control. Changing the power levels of the reverse communication links by the mobile station to transmit information to serving BTSs is referred to as reverse power control.
In a typical CDMA system, when entering the boundary region between base transceiver stations, a mobile station transitions from communicating with one base transceiver station to communicating with both base transceiver stations simultaneously. Thus, the communication is not interrupted and the speech quality is not degraded, even temporarily. This multiple link communication is commonly referred to as soft-hand off. Significant diversity benefit is derived by the mobile station due to the receiving and combining of multiple signal paths from the serving base station storing soft-hand off, thereby allowing a net drop in forward link power. Soft-hand off can involve two or more BTSs.
It is important to the proper and efficient operation of such systems that critical system-level information such as signaling frames be efficiently and reliably conveyed at low error rates so that system controls may be implemented as expeditiously as possible.